fuzz: Pass down MAKEJOBS to test_runner

ci/test/06_script_b.sh

@@ -43,6 +43,6 @@ fi
 
 if [ "$RUN_FUZZ_TESTS" = "true" ]; then
   BEGIN_FOLD fuzz-tests
-  DOCKER_EXEC test/fuzz/test_runner.py ${FUZZ_TESTS_CONFIG} -l DEBUG ${DIR_FUZZ_IN}
+  DOCKER_EXEC test/fuzz/test_runner.py ${FUZZ_TESTS_CONFIG} $MAKEJOBS -l DEBUG ${DIR_FUZZ_IN}
   END_FOLD
 fi

test/fuzz/test_runner.py

@@ -38,6 +38,7 @@ def main():
     )
     parser.add_argument(
         '--par',
+        '-j',
         type=int,
         default=4,
         help='How many targets to merge or execute in parallel.',